Ontario Pesticide Training and Certification CORE Practice Exam

What is oral LD50?

The amount of substance (mg/kg body weight) that kills 50% of test animals when ingested

LD50 is the amount of a substance that will lethally affect 50% of a test population, expressed as mg of substance per kg of body weight. When we specify oral LD50, we’re talking about the dose that must be swallowed to cause death in 50% of the animals. The route of exposure changes how a substance is absorbed and processed by the body, so the oral route is distinct from dermal or inhalation routes. Ingestion passes through the gut and liver before reaching the rest of the body, which can alter toxicity compared with contact through the skin or breathing in the substance. So the oral LD50 is the measure of acute toxicity for ingestion, reflecting how dangerous swallowing the substance is. A low oral LD50 means high acute toxicity by ingestion, while a higher value means lower acute toxicity via swallowing.

The amount of substance (mg/kg body weight) that kills 50% of test animals when applied to skin

The amount of substance (mg/kg body weight) that kills 50% of test animals when inhaled

The amount of substance (mg/kg body weight) that kills 50% of test animals when absorbed through mucous membranes